Rubber composition, vulcanizate, and air intake hose

ABSTRACT

A rubber composition, including α,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (A) having number average molecular weight of 50,000 to 150,000, α,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber (B) having number average molecular weight of 1,000 to 20,000, ethylene-α-olefin copolymer rubber (C), and a graft copolymer (D); wherein said graft copolymer (D) is obtained by performing graft copolymerization on a mixture of an aromatic vinyl compound and an α,β-ethylenically unsaturated nitrile monomer with an ethylene-propylene-unconjugated copolymer, and a content of structure units of said ethylene-propylene-unconjugated copolymer is 20 to 70 wt %; a ratio of the graft copolymer (D) with respect to 100 parts by weight in total of said rubber (A), rubber (B) and rubber (C) is 1 to 30 parts by weight; and a composition ratio of the rubber (A), rubber (B) and rubber (C) is rubber (A): 20 to 79 wt %, rubber (B): 1 to 30 wt %, and rubber (C): 20 to 50 wt %, is subjected to vulcanization molding, consequently, vulcanizate of the rubber composition having excellently balanced ozone resistance, flexing fatigue resistance and oil resistance can be provided.

This application is a Divisional of co-pending Application No.10/829,228, filed on Apr. 22, 2004, the entire contents of which arehereby incorporated by reference and for which priority is claimed under35 U.S.C. §120.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rubber composition comprisingα,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubberand ethylene-α-olefin copolymer rubber as main components, a vulcanizateof the rubber composition, and air intake hose composed of thevulcanizate.

2. Description of the Related Art

As a rubber material having oil resistance and ozone resistance at atime, chloroprene rubber is conventionally known. However, since thechloroprene rubber includes chlorine, it may bring an environment issue.Accordingly, as a substitution of the chloroprene rubber, a rubbercomposition of α,β-ethylenically unsaturated nitrile-conjugated dienecopolymer rubber and ethylene-α-olefin copolymer rubber has beenstudied. However, they are not dissolved to each other when kneadingonly these two kinds of rubbers, so that vulcanizate to be obtained isexcellent in ozone resistance but poor in mechanical strength andflexing fatigue resistance.

Accordingly, there has been a proposal of blending chlorinatedpolyethylene as a compatibilizing agent in the composition ofα,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubberand ethylene-α-olefin copolymer rubber (refer to the patent article 1).

However, the vulcanizate obtained by vulcanizing the compositiondescribed in the patent article 1 has excellent mechanical strength buthas insufficient flexing fatigue resistance. Also, since it includeschlorine, it may bring an environment issue.

Also, there has been disclosed (refer to the patent article 2) a rubbercomposition which can improve heat resisting durability and oilresistance, etc. by adding a specific graft polymer toacrylonitrile-butadiene copolymer rubber (a subordinate concept ofα,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber)and ethylene-propylene copolymer rubber (a subordinate concept ofethylene-α-olefin copolymer rubber). The specific graft copolymerdisclosed in the patent article 2 is obtained by performing graftcopolymerization on a mixture of an aromatic vinyl compound and a polarvinyl compound (a leading concept of an α,β-ethylenically unsaturatednitrile monomer) with an ethylene-propylene-unconjugated dienecopolymer.

Since the vulcanizate obtained by vulcanizing the composition describedin the patent article 2 does not include chloride, it does not bring anyenvironment issues but has a problem to be solved on flexing fatigueresistance.

Patent Article 1: the Japanese Unexamined Patent Publication No. 59(1984)-199737 Patent Article 2: the Japanese Unexamined PatentPublication No. 54 (1979)-106554

SUMMARY OF THE INVENTION

An object of the present invention is to provide a rubber compositionhaving excellently balanced ozone resistance, flexing fatigue resistanceand oil resistance and being suitable as an air intake hose material,vulcanizate of the rubber composition, and air intake hose composed ofthe vulcanizate.

The present inventors committed themselves to study to attain the aboveobjects, found that a rubber composition obtained by blending liquidα,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber(B) having small molecular weight and a graft copolymer (D) including aspecific amount of ethylene-propylene-unconjugated copolymer structureunits in addition to solid α,β-ethylenically unsaturatednitrile-conjugated diene copolymer rubber (A) having large molecularweight and ethylene-α-olefin copolymer rubber (C) has excellentlybalanced ozone resistance, flexing fatigue resistance, and oilresistance, and completed the present invention.

Namely, according to the present invention, there is provided a rubbercomposition, including

α,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber(A) having number average molecular weight of 50,000 to 150,000,

α,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber(B) having number average molecular weight of 1,000 to 20,000,

ethylene-α-olefin copolymer rubber (C), and

a graft copolymer (D),

wherein

the graft copolymer (D) is obtained by performing graft copolymerizationon a mixture of an aromatic vinyl compound and an α,β-ethylenicallyunsaturated nitrile monomer with an ethylene-propylene-unconjugatedcopolymer, and a content of structure units of theethylene-propylene-unconjugated copolymer is 20 to 70 wt %;

a ratio of the graft copolymer (D) with respect to 100 parts by weightin total of the rubber (A), rubber (B) and rubber (C) is 1 to 30 partsby weight; and

a composition ratio of the rubber (A), rubber (B) and rubber (C) is

rubber (A): 20 to 79 wt %,

rubber (B): 1 to 30 wt %, and

rubber (C): 20 to 50 wt %.

Preferably, the rubber composition further includes a vulcanizing agent.

According to the present invention, there is provided vulcanizateobtained by vulcanizing the above rubber composition.

According to the present invention, there is provided air intake hosecomposed of the above vulcanizate.

EFFECT OF THE INVENTION

As explained above, according to the present invention, a rubbercomposition having excellently balanced ozone resistance, flexingfatigue resistance and oil resistance and being suitable as an airintake hose material, a vulcanizate of the rubber composition, and airintake hose composed of the vulcanizate can be provided.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Rubber Composition

The rubber composition according to the present invention includes

α,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber(A) having number average molecular weight of 50,000 to 150,000,

α,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber(B) having number average molecular weight of 1,000 to 20,000,

ethylene-α-olefin copolymer rubber (C), and

a graft copolymer (D),

Note that, in the explanation below, the above α,β-ethylenicallyunsaturated nitrile-conjugated diene copolymer rubber (A) having numberaverage molecular weight of 50,000 to 150,000 will be referred to asrubber (A), the α,β-ethylenically unsaturated nitrile-conjugated dienecopolymer rubber (B) having number average molecular weight of 1,000 to20,000 will be referred to as rubber (B), and the ethylene-α-olefincopolymer rubber (C) will be referred to as rubber (C).

Rubber (A)

The rubber (A) used in the present invention is rubber obtained bycopolymerizing α,β-ethylenically unsaturated nitrile monomer with aconjugated diene monomer.

The number average molecular weight of the rubber (A) is 50,000 to150,000, preferably 60,000 to 120,000, more preferably 70,000 to 100,000in polystyrene conversion by gel permeation chromatography. When themolecular weight is excessively small, mechanical strength of thevulcanizate becomes poor, while when excessively large, workability ofthe rubber composition as a molding material becomes poor.

A content of α,β-ethylenically unsaturated nitrile monomer units in therubber (A) is preferably 25 to 60 wt %, more preferably 28 to 50 wt %,particularly preferably 33 to 45 wt %. When the content of theα,β-ethylenically unsaturated nitrile monomer units is excessivelysmall, oil resistance of the vulcanizate becomes poor in some cases,while when excessively large, mechanical strength of the vulcanizate ata high temperature declines in some cases. As the α,β-ethylenicallyunsaturated nitrile monomer, for example, acrylonitrile,methacrylonitrile, etc. may be mentioned, and acrylonitrile ispreferable.

As the conjugated diene monomer, 1,3-butadiene, isoprene,2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, etc. may be mentioned, and1,3-butadiene is preferable.

The rubber (A) may be copolymerized with other monomers than theα,β-ethylenically unsaturated nitrile monomer and the conjugated dienemonomer, which can be copolymerized with the two, within the range ofnot substantially inhibiting the effect of the present invention. Assuch a monomer, an unconjugated diene monomer, α-olefin monomer,α,β-ethylenically unsaturated mono carboxylic acid, α,β-ethylenicallyunsaturated polycarboxylic acid or anhydrites thereof may be mentioned.As the unconjugated diene monomer, those having the carbon number of 5to 12 are preferable and 1,4-pentadiene, 1,4-hexadiene, vinylnorbornene, dicyclopentadiene, etc, may be mentioned. As the α-olefin,those having the carbon number of 2 to 12 are preferable, and ethylene,propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene, etc.may be mentioned. As the α,β-ethylenically unsaturated mono carboxylicacid, acrylic acid, methacrylic acid, etc. may be mentioned. As theα,β-ethylenically unsaturated polycarboxylic acid, itaconic acid,fumaric acid, maleic acid, etc. may be mentioned. As theα,β-ethylenically unsaturated polycarboxylic acid anhydrite, itaconicanhydrite, maleic anhydrite, etc. may be mentioned.

Other than the above, the rubber (A) may be copolymerized with acopolymerizable antioxidant. As the copolymerizable antioxidant,N-(4-anilinophenyl) acrylamide, N-(4-anilinophenyl) methacrylamide,N-(4-anilinophenyl) cinnamamide, N-(4-anilinophenyl) crotonamide,N-phenyl-4-(3-vinylbenzyloxy)aniline, N-phenyl-4-(4-vinylbenzyloxy)aniline etc. may be mentioned.

A method of producing the rubber (A) is not particularly limited, and itmay be produced by performing copolymerization by a known method. Anemulsion polymerizing method is normally used. When producing the rubber(A) by the emulsion polymerizing method, polymerization is performed at0 to 50° C. in a deoxygenated reactor vessel. The above monomers, anemulsifying agent, initiator and molecular weight regulator, etc. areput in the reactor vessel to react. The monomers and emulsifying agentmay be added by the whole amount before the reaction, or may be added infractional amounts after starting the reaction. After the polymerizationreaction finishes, a coagulant is added to an emulsified polymerizationliquid including the rubber (A) to coagulate the rubber (A), and theresult is washed and dried for recovering.

Rubber (B)

The rubber (B) used in the present invention is a rubber obtained bycopolymerizing an α,β-ethylenically unsaturated nitrile monomer with aconjugated diene monomer.

The number average molecular weight of the rubber (B) is 1,000 to20,000, preferably 2,000 to 10,000, more preferably 3,000 to 7,000 inpolystyrene conversion of gel permeation chromatography. When themolecular weight of the rubber (B) is too small, mechanical strength ofthe vulcanizate becomes poor, while when too large, workability of therubber composition as a molding material and flexing fatigue resistanceof the vulcanizate become poor.

A content of α,β-ethylenically unsaturated nitrile monomer units in therubber (B) is preferably 15 to 60 wt %, more preferably 25 to 50 wt %,particularly preferably 30 to 45 wt %. When the content ofα,β-ethylenically unsaturated nitrile monomer units is too small, oilresistance and mechanical strength of the vulcanizate become poor insome cases, while when too large, mechanical strength of the vulcanizateat a high temperature becomes poor in some cases. As theα,β-ethylenically unsaturated nitrile monomer, a conjugated dienemonomer and a copolymerizable monomer with these to be used inaccordance with need, those explained as other monomers to be used forthe rubber (A) can be used, and preferable monomers are also the same.

A method of producing the rubber (B) is not particularly limited and itmay be produced by performing copolymerization by a well known method.Generally, an emulsion polymerizing method is preferably used. Whenproducing the rubber (B) by the emulsion polymerization method, the samemethod can be adopted as that in the case of producing the rubber (A) bythe emulsion polymerization method except that an amount of themolecular weight regulator and preferable amounts of the respectivemonomers used in the polymerization are different.

Note that a pH measured when a mixture obtained by mixing only therubber (A) and the rubber (B) to be the same composition as that in therubber composition of the present invention is dissolved in a mixturesolvent composed of tetrahydrofran and water under the given conditionsbelow is preferably 2 to 7, more preferably 3 to 5. When the value ofthe pH is too small, the vulcanizing speed of the rubber compositionbecomes slow to result in polluting a metal, etc. in some cases, whilewhen too large, flexing fatigue resistance of the vulcanizate becomespoor in some cases. The value of the pH is a value obtained by puttingan electrode of a pH meter in a solution, wherein 6 g of the mixture ofthe rubber (A) and the rubber (B) is dissolved in 100 g oftetrahydrofran, dropping 2 ml of distilled water while agitating, andmeasuring two minutes after finishing the dropping.

It is sufficient when the above pH value becomes a value in the abovepreferable range when measuring the mixture of the rubber (A) and therubber (B) by the above measurement method. A pH of each of the rubber(A) and rubber (B) measured by the above measurement method is notparticularly limited, but the pH measured by the above measurementmethod is preferably in a range of 2 to 7 and more preferably a range of3 to 5 in both of the rubber (A) and the rubber (B). When pHs of both ofthe rubber (A) and rubber (B) are in the above range, variation of thepH measured by the above measurement method due to variation of blendingratio of the two when preparing the rubber composition of the presentinvention can be made small, and production thereof becomes easy.

A pH value of the above mixture of the rubber (A) and the rubber (B) canbe adjusted by a kind and content of compounding agents, etc. andmonomer units included in the rubbers. To make the pH fall in the abovepreferable range, it is preferable that the rubber (A) and the rubber(B) are blended with an acidic substance or copolymerized with a monomerwhich becomes acidic in a solution. As the acidic substance,hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and otherinorganic acids; acetic acid, citric acid, succinate and other organicacids; aluminum sulfate, aluminum chloride, and other strong acid salts;a mixture of calcium chloride and sulfuric acid, a mixture of magnesiumsulfate and hydrochloric acid, and other mixtures of a neutral substanceand strong acid; etc. may be mentioned. All of these acidic substancesserve as a coagulant in emulsion polymerization. As the monomer becomingacidic, α,β-ethylenically unsaturated mono carboxylic acid,α,β-ethylenically unsaturated polycarboxylic acid, anhydrites ofα,β-ethylenically unsaturated polycarboxylic acid may be mentioned.

In the case of producing the rubber (A) and the rubber (B) by emulsionpolymerization, when coagulating by an acrylic coagulant, the pHmeasured by the above measuring method sometimes becomes alkali evenwhen the rubber (A) and the rubber (B) includes the above monomer unitsexhibiting acidic. In that case, it is preferable to use the aboveacidic substance as the coagulant.

The pH measured by the above measurement method changes in accordancewith a combination of a kind and amount of an acidic substance and amonomer exhibiting acidic. To adjust the pHs of the rubber (A) and therubber (B) to be in the above preferable range, it is necessary todetermine a polymerization condition, coagulation processing conditionand, if necessary, post-processing condition by a preliminaryexperiment, etc.

Rubber (C)

A rubber (C) used in the present invention is a rubber obtained bycopolymerizing ethylene, α-olefin and, if necessary, a monomer which canbe copolymerized with these.

The number average molecular weight of the rubber (C) is preferably50,000 to 500,000, more preferably 60,000 to 300,000, particularlypreferably 70,000 to 200,000 in polystyrene conversion by gel permeationchromatography. When the molecular weight is too small, mechanicalstrength of vulcanizate becomes poor, while when too large, workabilityof the rubber composition as a molding material becomes poor.

A content of the α-olefin unit of the rubber (C) is preferably 1 to 50wt %, more preferably 3 to 40 wt %, and particularly preferably 5 to 30wt %. When the content of the α-olefin unit becomes too large,mechanical strength of the vulcanizate becomes poor, while when toosmall, cold resistance becomes poor.

As the α-olefin, those having a carbon number of 3 to 20 are preferable,and 1-propen, isobutylene, 1-butene, 1-hexene, 4-methyl-1-pentene,1-octene, etc. may be mentioned.

The rubber (C) may be obtained by copolymerizing ethylene, α-olefin anda monomer which can be copolymerized with these within a range of notsubstantially inhibiting the effect of the present invention. As such amonomer, styrene, alkyl substituent styrene, and other aromatic vinylmonomers; butadiene, 1,4-hexadiene, dicyclopentadiene, and other dienemonomers; cyclopentene, cyclohexene, cyclooctene, and other cycloolefinmonomers may be mentioned.

A method of producing the rubber (C) is not particularly limited and itmay be produced by copolymerizing by a known method. A solutionpolymerization method is normally used.

Graft Copolymer (D)

A graft copolymer (D) used in the present invention is obtained byperforming graft copolymerization on a mixture of an aromatic vinylcompound and an α,β-ethylenically unsaturated nitrile monomer with anethylene-propylene-unconjugated diene copolymer.

As the aromatic vinyl compound, styrene, α-methyl styrene, nucleussubstitution styrene, etc. may be mentioned. Styrene is preferable amongthese.

As the α,β-ethylenically unsaturated nitrile monomer, acrylonitrile,methacrylonitrile, etc. may be mentioned. Acrylonitrile is preferableamong these.

A weight ratio of an aromatic vinyl compound and α,β-ethylenicallyunsaturated nitrile monomer in the mixture is preferably 90:10 to 30:70.Other monomer may be included in the mixture of an aromatic vinylcompound and α,β-ethylenically unsaturated nitrile monomer. As suchother monomers, methyl (metha)acrylate, hydroxyethyl (metha)acrylate andother (metha)acrylic esters, may be mentioned.

A graft polymerization method is not particularly limited and a knownmethod can be applied. Generally, a method of performing graftpolymerization by emulsion polymerization in the presence of latex of anethylene-propylene-unconjugated diene copolymer and a method ofdissolving an ethylene-propylene-unconjugated diene copolymer in anorganic solvent or an aromatic vinyl compound or α,β-ethylenicallyunsaturated nitrile monomer, etc. and performing graft polymerization inthe solution can be applied. Conditions of the polymerization are notparticularly limited, and known conditions are applied.

In the present invention, a content of ethylene-propylene-unconjugateddiene copolymer structure units in the graft copolymer (D) is 20 to 70wt %, preferably 25 to 65 wt %, and particularly preferably 30 to 60 wt%. When the content of ethylene-propylene-unconjugated diene copolymerstructure units is too small, flexing fatigue resistance of thevulcanizate cannot be improved, while when too large, oil resistance andozone resistance become poor. The rubber composition of the presentinvention is particularly characterized by the point that the content ofethylene-propylene-unconjugated diene copolymer structure units in thegraft copolymer (D) is limited to be within a specified range.

Ratio of Respective Components (Content in Rubber Composition)

In the rubber composition of the present invention, a ratio of the graftcopolymer (D) with respect to 100 parts by weight in total of the aboverubber (A), rubber (B) and rubber (C) is 1 to 30 parts by weight,preferably 2 to 20 parts by weight, particularly preferably 3 to 15parts by weight.

The composition ratio of the rubber (A), rubber (B) and rubber (C) isthe rubber (A) of 20 to 79 wt %, preferably 30 to 75 wt %, andparticularly preferably 40 to 70 wt %; the rubber (B) of 1 to 30 wt %,preferably 3 to 23 wt %, and particularly preferably 5 to 15 wt %; andthe rubber (C) of 20 to 50 wt %, preferably 22 to 47 wt %, andparticularly preferably 25 to 45 wt %.

When an amount of the rubber (A) is too small, oil resistance of thevulcanizate becomes poor in some cases, inversely, when too large, ozoneresistance becomes poor in some cases. When an amount of the rubber (B)is too small, flexing fatigue resistance of the vulcanizate becomes poorin some cases, inversely, when too large, mechanical strength becomespoor in some cases. When a content of the rubber (C) is too small, ozoneresistance of the vulcanizate becomes poor in some cases, inversely,when too large, oil resistance becomes poor in some cases. When anamount of the graft copolymer (D) is too small, mechanical strength ofthe vulcanizate becomes poor in some cases, inversely, when too large,hardness change at a high temperature becomes poor in some cases.

Vulcanizable Rubber Composition

In the present invention, a vulcanizable rubber composition can beobtained by blending a vulcanizing agent in the above rubbercomposition. As the vulcanizing agent, a sulfur-based vulcanizing agent,an organic peroxide, a polyamine-based vulcanizing agent, etc. may bementioned.

As the sulfur-based vulcanizing agent, sulfur powder, precipitatedsulfur and other sulfurs; 4,4′-dithiomorpholine, tetramethylthiramdisulfide, tetraethylthiram disulfide, polymer polysulfide and otherorganic sulfur compounds; etc. may be mentioned.

As the organic peroxide, dialkyl peroxides, diacyl peroxides, andperoxyesters, etc. may be mentioned. As the dialkyl peroxide, dicumylperoxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexine, 2,5-dimethyl-2,5-di(t-butyl peroxy)hexane,l,3-bis(t-butyl peroxyisopropyl)benzene, etc. may be mentioned. As thediacyl peroxide, benzoil peroxide and isobutyl peroxide, etc. may bementioned. As the peroxyester, 2,5-dimethyl-2,5-bis(benzoilperoxy)hexane, t-butyl peroxyisopropyl carbonate, etc.), etc. may bementioned.

A polyamine-based vulcanizing agent is a compound having two or moreamino groups wherein a plurality of hydrogen of fatty hydrocarbon andaromatic hydrocarbon are substituted to be an amino group or hydrazidestructure, that is, the structure expressed by CONHNH₂. As thepolyamine-based vulcanizing agent, fatty polyamines, aromaticpolyamines, compounds having two or more hydrazide structures may bementioned. As the fatty polyamines, hexamethylene diamine, hexamethylenediamine carbamate, tetramethylene pentamine, hexamethylenediamine-cinnamaldehyde addition product, hexamethylenediamine-dibenzoate salt, etc. may be mentioned. As the aromaticpolyamines, 4,4′-methylene dianiline, 4,4′-oxydiphenylamine,m-phenylenediamine, p-phenylenediamine, 4,4′-methylenebis(o-chloroaniline), etc. may be mentioned. As the compounds having twoor more hydrazide structures, dihydrazide isophthalate, adipic aciddihydrazide, sebacic acid dihydrazide, etc. may be mentioned.

A blending quantity of the vulcanizing agent differs in accordance witha kind of the vulcanizing agent, but preferably 0.1 to 10 parts byweight, more preferably 0.3 to 7 parts by weight, particularlypreferably 0.5 to 5 parts by weight with respect to 100 parts by weightof the rubber (A). When the blending quantity of the vulcanizing agentis too small, vulcanizing density of the vulcanizate becomes low and oilresistance becomes poor in some cases, while when too large, flexingfatigue resistance becomes poor.

When using a sulfur-based vulcanizing agent, it is normally preferableto use with a vulcanization accelerator. As the vulcanizationaccelerator, a zinc oxide, sulfonamide-based vulcanization accelerator,guanidine-based vulcanization accelerator, thiazole-based vulcanizationaccelerator, thiuram-based vulcanization accelerator, dithioic acid saltbased vulcanization accelerator, etc. may be mentioned. A use amount ofthe vulcanization accelerator is not particularly limited and may bedetermined in accordance with a use object of vulcanizate, requiredcapability, a kind of a sulfur vulcanizing agent, and a kind of thevulcanization accelerator, etc.

Also, when using an organic peroxide, it is normally preferable to usewith a vulcanization auxiliary. As the vulcanization auxiliary, triarylcyanurate, trimethylolpropane trimethacrylate, N,N′-m-phenylenebismaleimide, etc. may be mentioned. These may be dispersed in clay,calcium carbonate, silica, etc. to improve workability of a rubbercomposition for use. A use amount of the vulcanization auxiliary is notparticularly limited and may be determined in accordance with a useobject of vulcanizate, required capability, a kind of a vulcanizingagent, a kind of the vulcanization auxiliary, etc.

Other Compounding Agents

The rubber composition of the present invention may include acompounding agent used in general rubber, for example, carbon black,silica and other reinforcing agents; calcium carbonate, clay, talc,calcium silicate and other fillers; α,β-unsaturated metal carboxylate;plasticizers; pigments, etc. in a range of not substantially inhibitingthe effect of the present invention. Also, a rubber or resin other thanthe rubber (A), the rubber (B) and the rubber (C) may be included in arange of not substantially inhibiting the effect of the presentinvention.

Rubber Composition Preparation Method

A preparation method of the rubber composition of the present inventionis not particularly limited and it may be prepared by a generalpreparation method of a rubber composition in the same way as otherrubber compositions. It may be kneaded by using a sealed mixer or openroll, etc. Note that when blending a vulcanizing agent, vulcanizationauxiliary and vulcanization accelerator, etc., it is preferable to use amethod which hardly causes shearing heating so as not to progressingvulcanization while mixing. For example, it is preferable that aftermixing with a Bunbary mixer without blending a vulcanizing agent, thevulcanizing agent is blended to perform final mixing with a roll.

Vulcanizate

In the present invention, the above vulcanizable rubber composition canbe made to be vulcanizate by heating at a higher temperature than thevulcanization starting temperature of the vulcanizing agent included inthe rubber composition.

The vulcanization temperature is preferably 100 to 200° C., morepreferably 130 to 190° C., particularly preferably 140 to 180° C. ingeneral vulcanizing agents. When the temperature is too low, it isliable that the vulcanization time becomes too long or vulcanizationdensity becomes too low. When the temperature is too high, it is liablethat defective molding is caused.

Also, the vulcanization time differs in accordance with a vulcanizationmethod, vulcanization temperature and a molding shape of the rubbercomposition, etc., but a range of not shorter than one minute and notlonger than five hours is preferable in terms of vulcanization densityand production efficiency. Furthermore, there are cases where the insideis not sufficiently vulcanized even though the surface is vulcanizeddepending on the shape and size of the mold, so that secondaryvulcanization may be performed.

A heating method for vulcanizing may be suitably selected from methodsused for rubber vulcanization, such as press heating, vapor heating,oven heating and hot-air heating.

The above vulcanizate has excellently balanced ozone resistance, flexingfatigue resistance and oil resistance and has sufficient mechanicalstrength. Therefore, it is used as a roll, hose, belt, seal (forexample, inlet seal) and other industrial parts and preferable as acomponent of vehicle rubber parts, such as packing, fuel hose, airintake hose, air duct hose, boot material (for example, CVJ bootmaterial), oil seal, and vehicle interior parts.

Air Intake Hose

Air intake hose according to the present invention is composed of theabove vulcanizate. The structure is not particularly limited, notlimited to a single layer and may be a multilayer structure having twoor more layers, such as other rubber layer and resin layer.

A method of producing the air intake hose according to the presentinvention is not particularly limited and it is produced by aconventionally known method. Preferably, it is produced by molding avulcanizable rubber composition including the above vulcanizate to behose having a predetermined shape by a conventionally known moldingmethod, such as injection molding and extrusion molding, and vulcanizingby steam vulcanization or other method.

EXAMPLES

Below, the present invention will be explained specifically by examplesand comparative examples. Parts and percentages below are based onweight unless otherwise mentioned.

Example 1

The rubber (A) was produced as below. 100 parts of a monomer mixture(55% of butadiene and 45% of acrylonitrile), 200 parts of ion-exchangewater, 3 parts of sodium dodecylbenzenesulfonate (an emulsifying agent),0.2 part of sodium sulfate, 0.3 part of potassium persulfate (apolymerization initiator) and 0.5 part of tert-dodecylmercaptan (amolecular weight regulator) are put in an autoclave replaced withnitride, brought to react at a reaction temperature of 30° C. until theinversion rate of the monomer reaches 85%, and the reaction was stoppedby adding 0.5 part of N,N diethyl hydroxylamine. The emulsionpolymerization reaction liquid was taken out, blew with steam at 100° C.to remove an unreacted monomer. 280 parts of the thus obtained emulsionpolymerization liquid was added to 1000 parts of 0.5% aluminum sulfatewater solution to coagulate copolymer rubber. The coagulation wassufficiently washed, dried at about 80° C. for 3 hours, so that 98 partsof acrylonitrile-butadiene copolymer rubber (A) having a number averagemolecular weight of 81,000 was obtained. An electrode of a pH meter wasplaced in a solution obtained by dissolving 6 g of the copolymer rubberin 100 g of tetrahydrofurane, 2 ml of distilled water was dropped whileagitating, then, the pH was measured after 2 minutes from completion ofthe dropping, which was 4.2. Note that the number average molecularweight was measured by gel permeation chromatography by usingtetrahydrofurane as a solvent as a standard polystyrene conversionvalue. The same procedure was taken for the later explained rubber (B).

The rubber (B) was produced as below. 100 parts of a monomer mixture(67% of butadiene and 33% of acrylonitrile), 200 parts of ion-exchangewater, 5 parts of sodium dodecylbenzenesulfonate (an emulsifying agent),0.2 part of sodium sulfate, 0.3 part of potassium persulfate (apolymerization initiator) and 8 part of tert-dodecylmercaptan (amolecular weight regulator) were put in an autoclave replaced withnitride, brought to react at a reaction temperature of 30° C. until theinversion rate of the monomer reaches 90%, and the reaction was stoppedby adding 0.5 part of N,N diethyl hydroxylamine. The emulsionpolymerization reaction liquid was taken out, blew with steam at 100° C.to remove an unreacted monomer. 280 parts of the thus obtained emulsionpolymerization liquid was added to 1000 parts of 0.5% aluminum sulfatewater solution to coagulate copolymer rubber. The coagulation wassufficiently washed, dried at about 80° C. for 3 hours, so that 98 partsof acrylonitrile-butadiene copolymer rubber (B) having a number averagemolecular weight of 3,000 was obtained. An electrode of a pH meter wasplaced in a solution obtained by dissolving 6 g of the copolymer rubberin 100 g of tetrahydrofurane, 2 ml of distilled water was dropped whileagitating, then, the pH was measured after 2 minutes from completion ofthe dropping, which was 4.2.

The graft copolymer (D) was produced as below. 100 parts of toluenesolution, wherein 50 parts of an ethylene-propylene-unconjugated dienecopolymer (the product number EPT4070 made by Mitsui Chemicals) wasuniformly dissolved in advance, was put in an auto clave substituted bynitride. 30 parts of styrene, 20 parts of acrylonitrile and 1 part ofbenzoyl peroxide (a radical initiator) were added thereto, and graftpolymerization reaction was brought at 60° C. for 10 hours, furthermore,the temperature was raised to 70° C. for two hours. The polymerizationrate was 95%. Toluene and a residual polymer were removed from theobtained solution by steam distillation, solidified products were finelypulverized, then, dried at 60° C. for 24 hours, and a graft copolymer(D) including an ethylene-propylene-unconjugated diene copolymer by acontent (content of EPDM in table 1) of 50% was obtained.

Note that as the rubber (C), ethylene-propylene-conjugated diene rubber(EPT 4070 made by Mitsui Chemicals: an ethylene unit content of 68 mol%, iodine value of 22, and number average molecular weight of 90,000)was used.

In addition to 60 parts of the rubber (A), 10 parts of the rubber (B),30 parts of the rubber (C) and 5 parts of the graft copolymer (D)obtained as above, 40 parts of carbon black (SIEST 3 made by TokaiCarbon CO., Ltd.), 5 parts of a plasticizer (dibutyl diglycol adipate:ADK CIZER RS-107 made by Asahi Denka Co., Ltd.), 1 part of stearic acid,5 parts of a zinc oxide (zinc oxide No. 1 made by SEIDO CHEMICALINDUSTRY CO., LTD.), 5 parts of naphthenic oil (Sunthene 415 made byJapan Sun Oil Co., Ltd.: a softener), and 1 part of diphenylaminederivatives (Antage OD made by Kawaguchi Chemical Industry Co., Ltd.: ananti-oxidant) were used to produce a rubber composition for air intakehose by kneading by a B-type Bunbary mixer for 5 minutes at 50° C.

The thus obtained rubber composition was blended with 1 part of sulfur(transmitted through 325 mesh), 2 parts of N-cyclohexyl-2-benzothiazolylsulfenic amide (a vulcanization accelerator), and 0.2 part oftetraethylthiram disulfide (a vulcanization accelerator) and subjectedto roll kneading at 50° C., so that a vulcanizable rubber compositionwas prepared.

The vulcanizable rubber composition was subjected to press vulcanizationunder conditions at 160° C. for 20 minutes with a pressing pressure of10 MPa, and a vulcanized sheet for test having a thickness of 2 mm wasproduced. Ozone resistance, flexing fatigue resistance and oilresistance were evaluated by using the vulcanized sheet. The results areshown in Table 1.

The ozone resistance was evaluated by producing based on the JIS-K6259 atest piece described in the section JIS4 thereof, holding the same underan environment of 40° C. with ozone concentration of 80 ppm and beingstretched by 40%, observing a crack arising condition after 72 hours,144 hours and 280 hours from starting of the above held state byfollowing the table 1 (state of cracks) in the JIS-K6259. The less thelater explained cracks arise, the more superior in ozone resistance. Theevaluation was indicated by abbreviations below. NC: no cracks wereobserved. A2 and B2: the alphabets indicate the number of cracks, thatis, B is larger than A and C is larger than B. The larger the number,the larger the size of cracks is. Cut: crack became large to cut thetest vulcanized sheet.

The flexing fatigue resistance was evaluated by producing a test pieceby following the section 5.3 in the JIS-K6260, repeating bending byfollowing the section 5.2.1, and counting the bending times until thetest piece was cut. The larger the bending times is, the more superiorin flexing fatigue resistance.

The oil resistance was evaluated by soaking the test vulcanized sheet ina test oil (IRM 903) adjusted at 100° C. by following the JIS-K6258, andobtaining the volume swelling degree ΔV (unit: %) after 70 hours. Theless the volume swelling degree is, the more superior in oil resistance.

Example 2

Except for using a graft copolymer (D), wherein a content of anethylene-propylene-unconjugated diene copolymer was 35%, produced bychanging the use amount of an ethylene-propylene-unconjugated dienecopolymer to 35 parts and the use amount of the mixture of styrene andacrylonitrile (styrene:acrylonitrile=30:20/weight ratio) to 65 parts,evaluation was made in the same way on ozone resistance, flexing fatigueresistance and oil resistance by using a vulcanized sheet produced inthe same way as in the example 1. The results are shown in Table 1.

Example 3

Except for using a graft copolymer (D), wherein a content of anethylene-propylene-unconjugated diene copolymer was 60%, produced bychanging the use amount of an ethylene-propylene-unconjugated dienecopolymer to 60 parts and the use amount of the mixture of styrene andacrylonitrile (styrene:acrylonitrile=30:20/weight ratio) to 40 parts,evaluation was made in the same way on ozone resistance, flexing fatigueresistance and oil resistance by using a vulcanized sheet produced inthe same way as in the example 1. The results are shown in Table 1.

Example 4

Other than changing to 50 parts of the rubber (A), 15 parts of therubber (B), 35 parts of the rubber (C) and 10 parts of the graftcopolymer (D), evaluation was made in the same way on ozone resistance,flexing fatigue resistance and oil resistance by using a vulcanizedsheet produced in the same way as in the example 1. The results areshown in Table 1.

Example 5

Other than using as the rubber (B) acrylonitrile-butadiene copolymerrubber having number average molecular weight of 10,000 obtained bychanging the amount of tert-dodecylmercaptan to 12 parts, evaluation wasmade in the same way on ozone resistance, flexing fatigue resistance andoil resistance by using a vulcanized sheet produced in the same way asin the example 1. The results are shown in Table 1.

Comparative Example 1

Except for using a graft copolymer (D), wherein a content of anethylene-propylene-unconjugated diene copolymer was 15%, produced bychanging the use amount of an ethylene-propylene-unconjugated dienecopolymer to 15 parts and the use amount of the mixture of styrene andacrylonitrile (styrene:acrylonitrile=30:20/weight ratio) to 85 parts,evaluation was made in the same way on ozone resistance, flexing fatigueresistance and oil resistance by using a vulcanized sheet produced inthe same way as in the example 1. The results are shown in Table 1.

Comparative Example 2

Except for using a graft copolymer (D), wherein a content of anethylene-propylene-unconjugated diene copolymer was 75%, produced bychanging the use amount of an ethylene-propylene-unconjugated dienecopolymer to 75 parts and the use amount of the mixture of styrene andacrylonitrile (styrene:acrylonitrile=30:20/weight ratio) to 25 parts,evaluation was made in the same way on ozone resistance, flexing fatigueresistance and oil resistance by using a vulcanized sheet produced inthe same way as in the example 1. The results are shown in Table 1.

Comparative Example 3

Except that the graft copolymer (D) was not added, evaluation was madein the same way on ozone resistance, flexing fatigue resistance and oilresistance by using a vulcanized sheet produced in the same way as inthe example 1. The results are shown in Table 1.

Comparative Example 4

Except that the rubber (B) was not added, evaluation was made in thesame way on ozone resistance, flexing fatigue resistance and oilresistance by using a vulcanized sheet produced in the same way as inthe example 1. The results are shown in Table 1. TABLE 1 ExampleComparative Example 1 2 3 4 5 1 2 3 4 Content of Rubber (A) 60 60 60 5060 60 60 60 70 Number Average Molecular Weight of Rubber (A) 81000 8100081000 81000 81000 81000 81000 81000 81000 Content of Rubber (B) 10 10 1015 10 10 10 10 0 Number Average Molecular Weight of Rubber (B) 3000 30003000 3000 10000 3000 3000 3000 3000 Content of Rubber (C) 30 30 30 35 3030 30 30 30 Content of Graft Copolymer (D) 5 5 5 10 5 5 5 0 5 Content ofEPDM in Graft Copolymer (D) 50 35 60 50 50 15 75 0 50 Ozone Resistance72(hr) NC NC NC NC NC NC NC NC NC 144(hr) NC NC NC NC NC NC NC A2 A2280(hr) NC NC NC NC NC A1 A1 A2 A2 Flexing Fatigue Resistance BendingTimes 100000 80000 90000 150000 80000 40000 80000 80000 10000 OilResistance Volume Swelling DegreeΔV(%) 58 56 60 63 58 55 62 55 55

As shown in Table 1, the comparative example 1 using a graft copolymer(D), wherein a content of the ethylene-propylene-unconjugated dienecopolymer was below the range of the present invention, was confirmed tohave excellent oil resistance, but the ozone resistance and the flexingfatigue resistance were not sufficient. Also, the comparison example 2using a graft copolymer (D), wherein a content of theethylene-propylene-unconjugated diene copolymer was above the range ofthe present invention, was confirmed to have excellent flexing fatigueresistance, but oil resistance and ozone resistance were insufficient.

Furthermore, it was confirmed that the comparative example 3 notincluding the graft copolymer (D) exhibited poor ozone resistance, andthe comparative example 4 not including the rubber (B) exhibited poorozone resistance and flexing fatigue resistance.

On the other hand, the examples 1 to 5, wherein the content of theethylene-propylene-unconjugated diene copolymer was within the range ofthe present invention, were confirmed to have excellently balanced ozoneresistance, flexing fatigue resistance and oil resistance.

The embodiments explained above are for easier understanding of thepresent invention and not to limit the present invention. Accordingly,respective elements disclosed in the above embodiments includes allmodifications in designs and equivalents belonging to the technicalfield of the present invention.

1. A vulcanizate obtained by vulcanizing a rubber composition, includingα,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber(A) having number average molecular weight of 50,000 to 150,000;α,β-ethylenically unsaturated nitrile-conjugated diene copolymer rubber(B) having number average molecular weight of 1,000 to 20,000;ethylene-α-olefin copolymer rubber (C); a graft copolymer (D); and avulcanizing agent wherein said graft copolymer (D) is obtained byperforming graft copolymerization on a mixture of an aromatic vinylcompound and an α,β-ethylenically unsaturated nitrile monomer with anethylene-propylene-unconjugated copolymer, and a content of structureunits of said ethylene-propylene-unconjugated copolymer is 20 to 70 wt%; a ratio of the graft copolymer (D) with respect to 100 parts byweight in total of said rubber (A), rubber (B) and rubber (C) is 1 to 30parts by weight; and a composition ratio of the rubber (A), rubber (B)and rubber (C) is rubber (A): 20 to 79 wt %, rubber (B): 1 to 30 wt %,and rubber (C): 20 to 50 wt %.
 2. Air intake hose composed of thevulcanizate as set forth in claim 1.